Ion generator and projector



c. G. BACON 2,736,809

ION GENERATOR AND PROJECTOR Feb. 28, 1956 Filed Nov. 6, 1945 INVENTOR. (onrad d. flacwz. BY

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Unite tates Patent l ION GENEnAroa AND PROJECTOR Conrad G. Bacon, Oak Ridge, Tenn, assignor, by mesne assignments, to the United States of America as represented by the United States Atomic Energy Commission Application November a, 1945, Serial No. 627,074

8 Claims. (Cl. 250-413) This invention relates to ion sources, that is, devices for producing ions and causing them to be projected in beam form. The invention is primarily directed to producing quantities of ions of the metal uranium. The invention may be adapted for various uses, but it finds a primary and advantageous application in isotope separating or segregating apparatus of the electromagnetic type as disclosed in a prior application of Ernest 0. Lawrence, Sr. No. 557,784, filed October 9, 1944, now U. S. Patent No. 2,709,222 issued May 24, 1955.

Various types of ion sources have been proposed in the past for use in the type of isotope separating apparatus described in the Lawrence application. Most of the dilferent types have certain drawbacks and disadvantages, and it is the object of my invention to provide a source characterized particularly by being free of the drawback of vapor of the material being ionized condensing on various parts, and otherwise crudding up the equipment.

Another object of the invention is to provide an ion source as described in the foregoing wherein an arc is struck between two electrodes formed of uranium, one of them having an opening therethrough, through which the ions are projected in beam form.

Another. object of the invention is to provide an ion source embodying two electrodes between which an arc is struck, the anode being a stick electrodeand the cathode having an opening therethrough so that the ions are projected through the opening in beam form.

Another object of the invention is to provide an ion source as in the previous objects wherein the stick electrode is provided with artificial cooling to prevent melting thereof.

Another object of the invention is to provide an ion source as in the previous objects having a collimating electrode, an accelerating electrode and a decelerating electrode, and a pair of deflection plates having alternating potential thereon for sweeping the ion beam so that the deflection plates constitute a virtual slit corresponding to the slit ordinarily employed in isotope separating apparatus as described in the earlier Lawrence application.

Further objects and numerous of the advantages of my invention will become apparent in the following detailed description and annexed drawing, the single figure of which represents diagrammatically a form of my invention.

Referring to the drawing, numeral 1 designates a stick electrode made of uranium, and it is within a sleeve 2 provided with artificial cooling as represented by coils 4 which may be supplied with cooling medium from any suitable source. Numeral 5 designates another electrode adjacent the stick electrode 1, the electrode 5 being round as shown and having a central opening 7 aligned with the stick electrode 1. The side of electrode 5 away from the electrode 1 is flat, and the side toward the electrode 1 has a hemispherical contour. The electrode 1 is grounded as shown and there is a poten- 2,736,809 Patented Feb. 28, 1956 ice tial of 500 volts, for example, impressed between the electrode 1 and electrode 5, electrode 5 being negative relative to electrode 1. The voltage is supplied from an adjustable source 9. Any mechanical means of known type, such as rack and pinion gearing 17 and control shaft 18, may be utilized for bringing the electrode 1 into contact with the electrode 5 for striking the arc, and then withdrawing the electrode 1. Also the electrode 1 may be automatically fed by mechanical means as it burns away, as is well known in the art. The electrode 5 constitutes a cathode and the stick electrode 1 an anode, the stick electrode 1 being bombarded with electrons emitted from the electrode 5 while the arc is on. The bombardment causes particles to be vaporized from the stick electrode 1 and ionized, and the positive ions are attracted by the electrode 5 and caused to pass through the opening 7 to the left. The cooling coils 4 prevent the heat generating by the arc from melting the stick electrode 1 and vaporization of the uranium is held to a minimum. Material which vaporizes from the stick electrode 1 and which does not become ionized may deposit on the electrode 5 causing it to build up somewhat.

The numeral 10 designates a collimating electrode which is a flat circular member having a circular opening 11 in the center coaxially aligned with the opening 7 in electrode 5. Collimating electrode 10 collimates the ionized particles into beam form, the beam being a relatively dense pencil of ions traveling in straight lines. The collimating electrode 10 is maintained at a high negative potential of 60 kilovolts, for example, supplied by a voltage supply 8.

Numeral 13 designates an electrode which is cylindrical in form being slightly larger than the openings 11 and 7 in the electrodes 10 and 5 and having its longitudinal axis aligned therewith. The electrode 13 is maintained at a relatively high negative potential supplied by the power supply 8 through variable resistor 12. Before the arc is struck, that is, when no ion current is flowing, electrodes 10 and 13 are at the same negative potential of 60 kilovolts, for example. During operation of the ion source, the positive ion drain current to electrode 13 produces an IR drop across resistor 12 of 10 kilovolts, for example, so that the operating potential of electrode 13 is minus 50 kilovolts, for example.

Numeral 14 designates a decelerating electrode which is cylindrical in form being somewhat larger than the electrode 13, and having its longitudinal axis coaxial with that of electrode 13. The electrode 14 is maintained at a negative potential of 3S kilovolts, for example, supplied by an adjustable voltage supply'15.

Adjacent the decelerating electrode 14 and beyond it area pair of deflection plates 16 having impressed thereon an alternating 60 cycle voltage of 10 kilovolts, for example, which acts as a sweep to sweep the beam of ions between the two deflection plates. The concentrated beam of ions being projected is therefore caused to be displaced laterally so that the deflection plates constitute a virtual slit corresponding to the slit utilized in various types of isotope separating apparatus wherein vapor of the material to be ionized is emitted through a slit and is ionized in the vicinity thereof.

From the foregoing the operation of the invention and the significane of the arrangement will be readily appreciated by those skilled in the art. The are is struck directly between the electrodes formed of uranium, and the ionizing process can be made continuous by constantly feeding the stick electrode 1- at a suitable rate. Positive ions formed at the stick electrode 1 are drawn to electrode 5 by virtue of its 500 volt negative potential. They pass through the hole 7 in electrode 5 and are accelerated to the 60 kilovolt potential of greases el e At r pas ing through the hole 11 .in electrode 10, the positive ions are successively decelerated to the 50 kilovolt potential of electrode 13 and the 35 kilovolt potential of electrode 14, at which latter potential they proceed through the deflection plates 16. Condensation and deposit of vaporized material causing parts to become coated is minimized and tin-ionized material may collect on the cathode causing it to build up rather than the cathode disintegrating and gradually disappearing.

By using the deflection plates as described, their function is that of a virtual slit as in known types of isotope separating apparatus thereby converting the entering pencil ion beam into "an emergent elongated ribbonlike beam, such as is employed in the above referred to Lawrence patent.

The embodiment of my invention disclosed herein 'is representative of its preferred form. The disclosure is to be interpreted in an illustrative rather than a limiting sense, the scope of the invention being determined in accordance with the claims appended hereto.

1 claim:

1. An ion source comprising a cathode made of uranium containing compound aond an anode made of uranium containing compound, means for striking an arc between said cathode and said anode, whereby ions of uranium are produced, means for maintaining said cathode at a constant negative potential with respect to said anode, and means for causing ions to be projected from the ionizing region past the cathode in a direction away from the anode.

2. An ion source comprising a cathode and anode, both said cathode and said anode being made of a uranium containing compound, means for striking an are between said cathode and said anode, and said cathode having an opening therethrough so arranged that positive ions may be projected therethrough away from the anode the surface of said cathode which faces said anode being hemispherical.

3. An ion source comprising means for ionizing ma- 3 terial including a cathode and an anode and means for striking an arc therebetween, means for causing positive ions to be projected in concentrated beam form from the ionizing region past the cathode in a direction away from the anode and means comprising deflection plates having a low frequency alternating potential impressed thereon associated with the beam for sweeping it, said deflecting plates having a length which is a small fraction of the distance travelled by the ions in one cycle of said alternating potential.

4. An ion source comprising a cathode and an anode each being made of a uranium containing compound, means for maintaining said cathode at a negative potential with respect to said anode, means for striking an are between said cathode and said anode, said cathode having an opening therethrough, a collimating electrode, means for maintaining said collimating electrode at a relatively high negative potential with respect to said cathode, said collimating electrode being disposed adjacent said cathode and having an opening therein aligned with the opening in said cathode so that a beam of ions is caused to be projected through said openings, and means comprising a decelerating electrode adjacent said collimating electrode, said decelerating electrode having a negative potential impressed thereon smaller than the negative potential of said collimating electrode, said decelerating electrode also having an opening therethrough aligned with the opening in said cathode for accommodating the ion beam.

5. An ion source comprising an anode and a cathode, each being made of a material from which it is desired to produce positive ions, means for maintaining said cathode at a negative potential with respect to said anode, means for striking an are between said cathode and said anode, said cathode having an opening therethrough, a collimating electrode, means for maintaining said collimating electrode at a relatively high negative potential with respect to said cathode, said collimating electrode being disposed adjacent said cathode and having an opening therein aligned with the opening in said cathode so that a beam of ions is caused to be proected through said openings, and means comprising a decelerating electrode adjacent said collimating electrode, said decelerating electrode having a negative potential impressed thereon smaller than the negative potential of said collimating electrode, said decelerating electrode also having an opening therethrough aligned with the opening in said cathode for accommodating the ion beam.

6. An ion source comprising a hollow cathode and an elongated solid anode, each containing material from which it is desired to produce ions, said cathode having a convex surface facing said anode, said anode having cooling means associated therewith, means for maintaining said cathode at a constant negative potential with respect to said anode, a ring shaped collimating electrode adjacent said cathode, means for maintaining said collimating electrode at a negative potential higher than said cathode, a ring shaped decelerating electrode adjacent said collimating electrode, and means for maintaining said decelerating electrode at a potential which is intermediate the negative potential of said cathode and said collimating electrode, all of said electrodes being axially aligned.

7. An ion source comprising a cathode having a central aperture extending therethrough, said cathode having one fiat surface and one hemispherical surface, an anode facing the hemispherical surface of said cathode, said anode and said cathode each containing material from which it is desired to produce ions, means for striking an are between said cathode and said anode, whereby ions of said material are produced, means for causing said ions to be projected from the ionizing region past the cathode in a direction away from the anode, said ions being in the form of a beam, and means comprising deflection plates having an alternating potential impressed therebetween associated with the ion beam for sweeping it. s

8. An ion source comprising a cathode and an anode, each containing material from which it is desired to produce ions, means for striking an arc between said cathode and said anode, whereby ions of said material are produced, means for maintaining said cathode at a constant negative potential with respect to said anode, and means for causing ions to be projected from the ionizing region past the cathode in a direction away from the anode.

References Cited in the file of this patent UNITED STATES PATENTS 2,064,469 Haetf Dec. 15, 1936 2,153,269 Nicoll Apr. 4, 1939 2,176,199 Biggs Oct. 17, 1939 2,331,189 Hipple Oct. 5, 1943 2,472,870 Washhurn June 14, 1949 OTHER REFERENCES Smythe: Physical Review, December 1926, vol. 28, pp. 1275-1286.

Dempster: Review of Scientific Instruments, J an. 1936, vol. 7, pp. 46-49. 

1. AN IN SOURCE COMPRISING A CATHODE MADE OF URANIUM CONTAINING COMPOUND AND AN ANODE MADE OF URANIUM CONTAINING COMPOUND, MEANS FOR STRIKING AN ARC BETWEEN SAID CATHODE AND SAID ANODE, WHEREBY IONS OF URANIUM ARE PRODUCED, MEANS FOR MAINTAINING SAID CATHODE AT A CONSTANT NEGATIVE POTENTIAL WITH RESPECT TO SAID ANODE, AND MEANS FOR CAUSING IONS TO BE PROJECTED FROM THE IONIZING REGION PAST THE CATHODE IN A DIRECTION AWAY FROM THE ANODE. 